Rope or chain rupture safety device

ABSTRACT

A rope or chain rupture safety device for a blowing lance secured to two ropes or chains, respectively, of which one rope or chain is passed over a driven main drum and the other rope or chain is passed over an unstressed auxiliary drum, the auxiliary drum being connected with said main drum by means of a multiplate friction clutch arranged between them and rotatable relative to said main drum in case of a rope or chain rupture, in which the improvement resides in that the auxiliary drum comprises an element which is rotatable relative to the main drum, connected with the shaft of the main drum by screw threaded means and screwable towards the friction clutch under progressively increasing engagement pressure of the plates of the friction clutch. This design is simple and safe. It affords the advantage that the auxiliary rope is loaded only with the double nominal load when the main rope breaks and that the initial braking moment may be lower by about one-third than so far.

United States Patent Schwarz et al,

[ 5] lFelb.29,119/72 [54] ROPE 0R CHAIN RUPTURE SAFETY DEVICE 3,366,3761/1968 Marino ..266/34 LM Schweng ..266/34 LM Schweng et al. ..266/34 LMPrimary Examiner-Gerald A. Dost Attorney-Kurt Kelman [5 7] ABSTRACT Arope or chain rupture safety device for a blowing lance secured to tworopes or chains, respectively, of which one rope or chain is passed overa driven main drum and the other rope or chain is passed over anunstressed auxiliary drum, the auxiliary drum being connected with saidmain drum by means of a multiplate friction clutch arranged between themand rotatable relative to said main drum in case of a rope or chainrupture, in which the improvement resides in that the auxiliary drumcomprises an element which is rotatable relative to the main drum,connected with the shaft. of the main drum by screw threaded means andscrewable towards the friction clutch under progressively increasingengagement pressure of the plates of the friction clutch. This design issimple and safe. It affords the advantage that the auxiliary rope isloaded only with the double nominal load when the main rope breaks andthat the initial braking moment may be lower by about onethird than sofar.

5 Claims, 3 Drawing Figures Patented Feb. 29, 1972 3,645,519

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AGENT ROPE 01R Cll-lAllN RIUWURE SAFETY lDlEl/lClE The invention relatesto a rope rupture safety device for a blowing lance secured to two ropesof which one rope is passed over a driven main drum and the other ropeis passed over an unstressed auxiliary drum, the auxiliary drum beingconnected with said main drum by means of a multiplate friction clutcharranged between them and rotatable relative to said main drum in caseof a rope rupture. The word rope" as used herein is understood tocomprise any kind of cordage, cables or chains as are conventional inhoisting technique.

A rope rupture safety device of this kind developed by applicants isdescribed in the U.S.A. Pat. No. 3,393,906 and in the British LettersPat. No. 1,064,309. In this device, in the event of a rope rupture, thefall of the lance is softly braked when a torque which is determined bythe prestress applied in the multiplate-clutch is exceeded, before arigid connection is effected between the main rope drum and theauxiliary drum by a ratchet catch.

The present invention is aimed at further developing and improving theknown device, and, more particularly, at increasing the engagementpressure of the plates and thus progressively increasing the brakingmoment in dependence on the relative movement between the auxiliary drumand the main drum in a manner that at the end of the rotation path thecushioning frictional engagement changes into a form locking connection.

A further aim of the invention resides in making it possible to adjustthe initial prestress of the springs, which prestress corresponds to theinitial braking moment, to be lower than so far, which affords theadvantage that, while the safety effect remains the same as before, theauxiliary rope or chain, respectively, may be dimensioned lighter thanup to now.

These aims of the invention are achieved in a rope or chain rupturesafety device of the kind described in the introduction in that oneelement of the auxiliary drum which is rotatable in relation to the maindrum is connected with the shaft of the main drum by means of a screwthread and may be screwed towards the friction clutch underprogressively increasing engagement pressure of the plates of thefriction clutch.

Advantageously, prestressed springs are provided between the element ofthe auxiliary drum which rotates with the auxiliary drum and is suitablydesigned as a disc, and the plates of the friction clutch, which springsare compressed when the disc is screwed towards the friction clutch.

According to a suitable embodiment of the invention the auxiliary drumis mounted to be rotatable on a shaft which is rigidly connected withthe main drum, the friction clutch, the rotatable element with athreaded sleeve and a pin fixed to the shaft and provided with acorresponding screw thread being arranged within the auxiliary drum.

For reasons of safety a stop may be provided for limiting the rotationpath of the auxiliary drum in relation to the main drum; for example amaximum rotation path of 360 may be provided, before the auxiliary drumgets into form-locking connection with the main drum by means of thestop.

In order that the invention may be more fully understood an embodimentthereof shall now be explained with reference to the accompanyingdrawings, in which FIG. 1 schematically shows a winch for a blowinglance with a rope or chain rupture safety device according to theinvention.

FIG. 2 is a vertical sectional view of the main and the auxiliary drums.

FIG. 3 illustrates the behavior of the plate friction moment withincreasing rotation angle of the auxiliary drum.

In FIG. 1 numeral 1 denotes a motor which drives the main drum 3 and theauxiliary drum via the gear 2. The main and the auxiliary drums aremounted in the bearing block 6 by means of a common shaft 5. The blowinglance 7 is fixed to a vehicle 8 movable in the guides 9 in verticaldirection by means of the winch. The load of the vehicle and of thelance is borne by the main rope l whereas the auxiliary rope llll isfixed to the spring biased suspension 12 and is idling with littleprestress. A trip cam 13 is provided at the spring-biased suspension 12,which trip cam actuates a limit switch 14 towards both sides in the caseof spring deflections which in turn causes the lifting motor l to beswitched off and braked.

In case of disturbances, i.e., when the rope MB is slack oroverstressed, elongated excessively or ruptures the spring of thesuspension 12 expands or is compressed, and thus actuates the finalswitch 14 which, in turn, causes the lifting and lowering movement tobestopped immediately. When the main rope 10 has been tom the load isfalling downward until the spring biased suspension 12 is completelypressed together and the entire load is received by the auxiliary rope11. Now the load is suspended on the auxiliary drum 4 and is to bebraked.

FIG. 2 serves to explain in detail how the multiplate friction clutchacting as a brake functions. The main drum 3 is flanged to the shaft end15 of the gear 2. It is provided with a proj ecting shaft 16 which ismounted on its far end in the bearing block 6 as has been describedabove. The auxiliary drum 4 is mounted to be rotatory in bearings 17 and18 on the shaft 16. By means of the friction clutch 119 it istorque-transmittingly connected with the shaft 16 and rotated with it.The friction clutch comprises a hub 20 which is wedged onto the shaftI6, the stop-disc 21, which is fixed to the hub by means of screws 22,and the clutch housing 23, which is screwed to the flange 25 of theauxiliary drum by means of screws 24. The friction plates 26 arearranged in the recess formed between the hub 20, the stop-disc 21 andthe clutch housing 23. The friction plates are acted upon byspring-biased rams or pistons 28. The springs 27 and the rams arearranged in bushings 29 and these bushings are disposed in bores of thepanel 30. This panel 30 is connected with an internally threaded sleeve31 which is rotatable or screwable axially in the direction of thearrows towards the friction plates 26 on a externally threaded pin 32 ofthe wedged-up hub. The panel 30 is connected by means of a tappet 33with the front wall 34 of the auxiliary drum 4 and axially displaceablerelative to it.

In the following it will be described how the device works: When themain rope it) breaks, the auxiliary rope ll is tightened, as has beendescribed earlier, and the auxiliary drum 4 is rotated against theresistance of the springs 27 and the friction between the frictionplates 26 relative to the main drum 3, so that the pressure force of thefriction plates is progressively increased in dependence on the rotationangle. The more the panel 30 is screwed on the threaded pin 32, i.e.,the more the panel 30 is displaced axially towards the friction clutch19, the more the tension of the springs 27 and thus the engagementpressure of the friction plates 26 is increased or the friction momentis enlarged.

In FIG. 3 the behavior of the friction moment M of the plates independence on the rotation angle 1; of the auxiliary drum isillustrated. At the beginning of the rotation the moment has a peakvalue (adherence moment M owing to the high adherence friction. Whensliding is started the moment decreases, as a result of the lowersliding friction, to the value M which is about half of M upon furtherrotation of the auxiliary drum M grows again to M owing to the increaseof the engagement pressure of the plates.

For reasons of safety it may be suitable to provide in addition for astop between the auxiliary drum and the main drum in order to limit thepossible rotation path. Such a stop is denoted with numeral 35 in H6. 2.The ropes may be fastened to the drums by means of clampingjaws 36.

The device according to the invention is superior to the known rope orchain rupture safety devices because it offers a number of advantages.The friction plates, which provide for the connection between the maindrum and the auxiliary drum need no longer be pressed together withconstant engagement pressure; thus, the initial braking moment (M inFIG. 3) may be adjusted to be lower by about 1/3 than so far which againis responsible for the fact that the adherence moment M becomes smallerin the same degree. in the device according to the invention theauxiliary rope is loaded when the initial impact occurs only with thedouble nominal load, whereas in the known devices the auxiliary rope hadto bear account for a threefold nominal load. With an equal dimension ofthe auxiliary rope a higher operational safety is thus gained. Since theactual braking moment depends on numerous factors some of which cannotbe evaluated at all, such as fatigue of the materia], ageing, varyingtemperature influences, changes in the friction value by environmentalfactors such as dust, dirt, humidity, it should be pointed out that inthe present invention these unsafety factors are completely eliminatedbecause the springs are automatically tightened when the auxiliary drumrotates and the braking moment is increased until the lance is broughtto a standstill in any case. Furthermore the device according to theinvention involves constructive simplifications over known devicesbecause such complicated parts as ratchet wheels and so on may be leftaway.

We claim:

l. A rope rupture safety device for a blowing lance secured to tworopes, whereof one rope is passed over a driven main drum and the otherrope is passed over an idling auxiliary drum connected with said maindrum through an interposed multiplate friction clutch and rotatablerelative to said main drum in the event of a rope rupture, saidauxiliary drum comprising an element which is rotatable relative to saidmain drum, connected to a projecting shaft portion of said main drum bymeans of a screw thread and screwable towards the friction clutch underprogressively increasing engagement pressure of the plates of thefriction clutch.

2. The safety device set forth in claim 1, wherein prestressed springsare provided between said element rotatable together with said auxiliarydrum and the plates of the friction clutch, which springs are pressedtogether when said element is screwed towards the friction clutch.

3. The safety device set forth in claim 1, wherein said element of saidauxiliary drum is designed as a disc.

4. The safety device set forth in claim 1, wherein said shaft portion onwhich the auxiliary drum is rotatable is rigidly fixed to said maindrum, the friction clutch, said rotatable element with a threadedsleeve, and a pin fixed to said shaft and provided with a correspondingscrew thread being arranged within the auxiliary drum.

5. The safety device set forth in claim 1, wherein a stop is providedfor limiting the rotation path of the auxiliary drum in relation to themain drum.

1. A rope rupture safety device for a blowing lance secured to tworopes, whereof one rope is passed over a driven main drum and the otherrope is passed over an idling auxiliary drum connected with said maindrum through an interposed multiplate friction clutch and rotatablerelative to said main drum in the event of a rope rupture, saidauxiliary drum comprising an element which is rotatable relative to saidmain drum, connected to a projecting shaft portion of said main drum bymeans of a screw thread and screwable towards the friction clutch underprogressively increasing engagement pressure of the plates of thefriction clutch.
 2. The safety device set forth in claim 1, whereinprestressed springs are provided between said element rotatable togetherwith said auxiliary drum and the plates of the friction clutch, whichsprings are pressed together when said element is screwed towards thefriction clutch.
 3. The safety device set forth in claim 1, wherein saidelement of said auxiliary drum is designed as a disc.
 4. The safetydevice set forth in claim 1, wherein said shaft portion on which theauxiliary drum is rotatable is rigidly fixed to said main drum, thefriction clutch, said rotatable element with a threaded sleeve, and apin fixed to said shaft and provided with a corresponding screw threadbeing arranged within the auxiliary drum.
 5. The safety device set forthin claim 1, wherein a stop is provided for limiting the rotation path ofthe auxiliary drum in relation to the main drum.